Abstract
M. Comm.
One function of skeletal muscle is to serve as the body's shock absorbers and thus
dampen rates of loading (ROL) around joints during activities. However, it is not clear
whether individuals with strong leg muscles actually demonstrate different ROL during
gait than weaker individuals. The aim of this cross-sectional study was to determine
the significance of muscle strength on ROL during gait. Females (ages 18 to 50) were
solicited via advertisement and screened via phone interviews. Subjects (n=56) were
chosen and placed into one of three groups based on training history: Strength Trained
(ST), Aerobically Trained (AT), and Sedentary (S). Subjects walked barefoot (10 trials)
over an 8 m walkway while ROL was sampled using a 1000 Hz force platform (AMTI
OR6-6). Gait speed was controlled between 2.22 - 2.45 m.s -1 using telemetric
photocells placed three meters apart. Maximum concentric and eccentric quadriceps
and hamstring strength were measured at 90 degrees•s -1 using an isokinetic
dynamometer (KINCOM 500H). Peak torque was divided by body weight to determine
relative strength (Nrn-kg -1 ). Statistical analyses (p<0.05) included ANOVA and the
Bonferroni/Dunn post-hoc test. There were no significant differences in age, height or
walking speed across groups. The S group (78.3 ± 15.6 kg, n=18) weighed significantly
more than the AT (60.5 ± 8.0 kg, n=19) and ST (63.1 ± 10.7 kg, n=19) groups. Body
composition analyses showed that the mean body fat percentage of the S group (34.8
± 7.3 %, n=18) was significantly higher than both AT (22.3 ± 5.7 %, n=19) and ST (23.2
± 6.9 %, n=19) groups. Relative concentric and eccentric strength of the quadriceps
of the AT (2.02 ± 0.07, n=19; 3.49 ± 0.18, n=19 respectively) and ST (2.1 ± 0.08, n=19;
3.50 ± 0.14, n=19 respectively) groups were significantly greater than the S (1.68 ±
0.07, n=18; 2.63 ± 0.10, n=18 respectively) group. Relative concentric hamstrings
strength of both the AT (1.07 ± 0.05, n=19) and ST (1.08 ± 0.04, n=19) groups were
significantly greater than the S (0.91 ± 0.04, n=18) group. Relative eccentric hamstring
strength of only the ST (1.60 ± 0.07, n=19) group was significantly greater than the
(1.34 ± 0.08, n=18) group. There were no significant differences in ROL between the
S (2.21 ± 0.15 %Wt.ms -1 , n=18) and AT groups (2.14 ± 0.15 %Wt-ms 1 , n=19) (p=0.70),
and the AT (2.14 ± 0.15 %Wt.ms-1 , n=19) and ST (1.82 ± 0.10 %Wt.ms -1 , n=19)
(p=0.10) groups. However, the females in the ST (1.82 ± 0.10 %Wt•ms -1 , n=19) group
had significantly lower ROL than the females in the S group. In addition, females in the
ST group demonstrated a lower frequency of heelstrike transient (HST) occurrence.
Seven of the S (n=18) females demonstrated HST while only four of the ST (n=19)
females did. In conclusion, strength trained females demonstrated significantly lower
rates of loading during gait than those in the sedentary group. High ROL have been
associated with knee pain and osteoarthritis. These findings suggest that strength
training may decrease the risk for these maladies.